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Gallic acid (GA) and formaldehyde condensation reaction was carried out under alkaline condition to prepare the gallic acid−formaldehyde resol resin (GAR). Obtained resin was used as adsorbent for recovery of palladium(II) and rhodium(III) ions from chloride-containing solutions. This kind of recovery was very simple and useful for generating little secondary wastes. Interaction of adsorption also was investigated: Chloropalladium(II) species were reduced to Pd(0), while hydroxyl groups of GAR were oxidized during the adsorption. Proposed adsorption of the aquachlororhodium(III) species mostly takes place via ligand exchange mechanism. GAR, Rh-adsorbed GAR, and Pd-adsorbed GAR were characterized by scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction spectroscopy, and Fourier transform infrared− attenuated total reflection spectroscopy.

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Linear and non-linear regression procedures have been applied to the Langmuir, Freundlich, Tempkin, Dubinin-Radushkevich, and Redlich-Peterson isotherms for adsorption of acid yellow 132 (AY132) dye onto red pine (Pinus resinosa) sawdust. The effects of parameters such as particle size, stirring rate, contact time, dye concentration, adsorption dose, pH, and temperature were investigated, and interaction was characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscope. The non-linear method of the Langmuir isotherm equation was found to be the best fitting model to the equilibrium data. The maximum monolayer adsorption capacity was found as 79.5 mg/g. The calculated thermodynamic results suggested that AY132 adsorption onto red pine sawdust was an exothermic, physisorption, and spontaneous process. Kinetics was analyzed by four different kinetic equations using non-linear regression analysis. The pseudo-second-order equation provides the best fit with experimental data.

Adsorption of gold and palladium species containing chlorine ion species onto commercial N-(2-[bis(2-aminoethyl)amino)ethyl]aminomethyl−polystyrene polymer beads (TRIS) was investigated. The influence of the pH, initial metal ion concentration, and contact time on the adsorption performance was examined in a batch adsorption experiment. To examine and discuss both the theoretical character of the metal ion adsorptions, Langmuir, modified Langmuir, Freundlich, Tempkin, Dubinin−Radushkevich, and nonlinear solutions of modified Langmuir and Redlich−Peterson isotherm models variables are calculated. The modified Langmuir monolayer adsorption capacities of the Pd(II) and Au(III) chlorine ions species were found to be 206.93 and 173.18 mg/g, respectively. The two metal adsorption kinetics fit the pseudo-second-order kinetic models. In thermodynamic calculations, the choice of different equilibrium constants with having a dimension is an important problem in the field. To overcome these problems, the modified Langmuir isotherm equilibrium constant was used for determination of thermodynamic parameters. Adsorption mechanism steps were characterized using Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The adsorbent is made to interact with each metal ion in the HCl solution electrostatic interaction and surface complex formation between the amine groups. The calculation of the thermodynamic parameters using the dimensionless modified Langmuir equilibrium constant was found to be more satisfying and reliable. Adsorptions of Pd(II) and Au(III) on TRIS beads were exothermic and endothermic spontaneous processes, respectively.

Abstract Many studies have examined metallic nanoparticles (NPs) produced according to the principles of green chemistry. Gold NPs have drawn much more attention than other metallic NPs in recent years. Moreover, among all gold NP synthesis studies, using plant-derived molecules is one of the commonly used reductants in studies on NP synthesis because of its convenience in terms of shape, size control advantage, and nontoxic specifications. The present review focused on studies of the synthesis of gold NP types, including single gold atom NPs, alloyed AU NPs, and core-shell Au NPs as well as their conditions and applications. The effect of those structures on application fields such as catalysis, antifungal action, antibacterial activities, sensors and so on are also summarized. Furthermore, the morphology and synthesis conditions of the primer and secondary NP were discussed. In addition to synthesis methods, characterization methods were analyzed in the context of the considerable diversity of the reducing agents used. As the reducing agents used in most studies, polyphenols and proteins usually play an active role. Finally, the challenges and drawbacks in plant-derived agent usage for the preparation of Au NPs at various industries were also discussed.